CHAPTER IL— SPECIFICATIONS NOW IN FORCE BY VARIOUS ASSOCIA- 

 TIONS. 



During the last few years a concerted effort has been made in this 

 country by various societies interested in wood preservation to adopt 

 uniform specifications for wood-preserving oils. Such specifications 

 have been adopted or have been proposed by several societies. In 

 addition to these, other specifications are still in force which do not 

 require all the latest tests. It is believed, however, that enough 

 of the more modern specifications are given in Table 36 to answer 

 most purposes; but, for the sake of simplification, only those are in- 

 cluded which apply to different types of oil. No claim is made for the 

 superiority of any of these oils. They differ only in boiling points. 

 Although it has been generally believed that the higher-boiling oils 

 are the most permanent, it has been shown that oils lighter than those 

 of specification No. 3, if used in a proper manner, have outlasted the 

 mechanical life of ties and poles. For land work, therefore, it seems 

 to be largely a matter of personal opinion as to which of these oils is 

 the best. It must be remembered that these specifications are for 

 materials of known origin and are in addition to the requirement that 

 the creosote shall be a coal-tar product. However, the tests given in 

 these specifications do not guarantee a pure coal-tar product. Cer- 

 tain selected materials which are not derived from coal tar may pass 

 all the tests; but the tests, if rigidly enforced, considerably reduce 

 the amount of such materials. At the same time, certain pure coal- 

 tar products are eliminated. The specification is intended to insure 

 the type of oil which has proved of benefit. Until other materials 

 have proved to be of value, or until our knowledge of the mechanism 

 of protection by creosote has been enlarged, it is deemed advisable to 

 exclude such materials from the best grade of oil, even though they 

 are coal-tar products. 



COAL-TAR SOLUTIONS. 



As already stated, tar solutions can not be considered so good pre- 

 servatives as pure coal-tar creosotes. They have not been in use 

 sufficiently long for their worth to be conclusively proved. It seems 

 reasonable, however, to expect that a mixture of coal tar and coal-tar 

 creosote wiU eventually be obtained that will preserve wood up to 

 the limit of its mechanical life. Just what proportion of creosote and 

 tar such a mixture will contain is problematical. Table 37 gives the 

 specifications for tar solutions now in force. 



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